1. Field of the Invention
For compatibilized polyphenylene ether-polyamide compositions which utilize certain polyfunctional compatibilizing compounds such as aliphatic polycarboxylic acids, it is possible to obtain improved impact strength and ductility by manufacturing an intermediate polyphenylene ether-polyamide compound utilizing a first polyamide component containing at least some nylon 6,6. The intermediate product is further compounded with a second polyamide component containing one or more polyamide resins different from nylon 6,6 or blends of such polyamide resins with nylon 6,6, to provide a compatibilized polyphenylene ether-polyamide composition having superior properties.
2. Brief Description of Related Art
Compatibilized polyphenylene ether-polyamide compositions have been provided utilizing a variety of base resins and compatibilizing systems. These thermoplastic products offer a wide range of beneficial properties which take advantage of the strengths of the basic resins while improving upon the weaknesses of each. Among the most useful properties of compatibilized polyphenylene ether-polyamide compositions are excellent heat resistance, chemical resistance, impact strength, hydrolytic stability and dimensional stability. Such compatibilized polyphenylene ether-polyamide compositions have found great utility in exterior automotive applications such as body panels. Examples of compatibilized polyphenylene ether-polyamide compositions can be found in U.S. patent application Ser. No. 736,490, filed May 20, 1985 and U.S. Pat. No. 4,315,086, both of which are hereby incorporated by reference.
The improved properties of polyphenylene ether-polyamide compositions have been achieved by providing a compatible combination of these normally incompatible resins.
A particularly useful series of compatibilized polyphenylene ether-polyamide products are based upon the combination of a polyphenylene ether, a polyamide resin (especially nylon 6,6) and a polyfunctional compatibilizing agent such as the aliphatic polycarboxylic acids (e.g. citric acid). When chemical resistance is important, the polyamide components will comprise at least 35 weight percent of the total composition, based upon the weight of the polyphenylene ether, the polyamide and any rubber impact modifier which may be used. This weight proportion will typically enable the polyamide to form a continuous phase as will the use of compatibilizing amounts of the polyfunctional compatibilizing agent.
It is believed that polyfunctional compatibilizing agents can facilitate formation of a graft copolymer of the polyphenylene ether and polyamide components. Such a reaction has been readily shown to take place under the time, temperature and shear conditions of typical thermoplastic extrusion processes. Graft copolymer produced in this fashion may serve as a melt surfactant which stabilizes the morphology of the resinous components of the system. Compatibility may also be achieved by improved interfacial adhesion of the resinous components.
Although compatibilized PPE/polyamide compositions utilizing nylon 6,6 offer many advantageous properties, compositions containing other polyamides are also sought. Compositions containing a nylon 6 component should benefit from reduced raw material cost as well as improved ductility. Experience has shown, however, that preparation of PPE/polyamide compositions containing nylon 6 and utilizing a polycarboxylic compatibilizing agent such as citric acid has been more difficult than preparation of PPE/polyamide compositions containing nylon 6,6. Generally, more severe compounding conditions are required to achieve acceptable properties.
It has now been discovered that PPE/polyamide compositions compatibilized with an aliphatic polycarboxylic acid compound and which contain a plurality of polyamide components have better impact strength and ductility compared to control compositions containing only one nylon component when manufactured in accordance with the process described below .